The present invention relates generally to a plastic closure for use with an associated container, and more particularly to an internally threaded plastic closure having at least one container-engaging stop element for limiting sealing engagement of the closure with the container, thereby facilitating venting of gas pressure from within the container, and removal of the closure from the container by consumers. The present invention also contemplates a method of packaging a hot-fill beverage which facilitates venting of gas pressure.
Threaded plastic closures have found very widespread application for use in connection with bottles and like containers by virtue of their economical manufacture and sealing performance. Closures of this nature typically include an outer plastic closure cap having an internal thread formation, and a sealing liner positioned adjacent the inside surface of a top wall portion of the outer cap. As the closure is threadingly applied to an associated container, the sealing liner is urged into sealing engagement with the sealing container. Threaded fitment of the closure to the container facilitates initial application of the closure, as well as re-application of the closure to the container by consumers after partial consumption of the container""s contents.
While closures of the above type have proven very commercially successful, over-application of the closures to containers can be problematic. When closures are applied to containers, either by high-speed capping equipment or by consumers, closures can be applied with a torque which exceeds that required for effecting the desired sealing engagement with the associated container. As will be appreciated, over-application can undesirably result in closures which are difficult for consumers to remove. This problem has been recognized in connection with closures having multi-lead thread formations, which are sometimes used on so-called xe2x80x9chot-fillxe2x80x9d beverages, that is, those filled at elevated temperatures. To control application, these types of closures typically have external marks (xe2x80x9cpull-upsxe2x80x9d) that are used with reference to marks on the container finish to indicate the degree to which the closure has been applied.
Apart from high removal torque, over-application of closures can be of concern in connection with the build-up of gas pressure within a container, such as the result of product fermentation caused by spoilage. Over-application of a closure can undesirably inhibit the closure""s venting characteristics. This occurs because the degree of sealing engagement between the closure and the container is beyond that which is necessary to achieve sealing integrity under normal conditions. As a consequence, deformation of the closure under the influence of internal gas pressure is insufficient to move the closure out of sealing engagement with the container.
The present invention is directed to an improved closure construction for a container which facilitates closure removal and venting of internal gas pressure by obviating problems associated with over-application of the closure.
A venting plastic closure embodying the principles of the present invention is particularly suited for use with an associated container having contents which ferment or otherwise spoil, resulting in the creation of internal gas pressure within the container. By virtue of the closure""s configuration, venting of gas pressure from within the container to acceptable levels is accommodated. The closure is configured to facilitate venting even in the event of over-application of the closure to the container, such as can occur attendant to the use of high-speed automated capping equipment, as well as facilitating convenient closure removal by consumers. A method of packaging a hot-fill beverage is also disclosed.
A venting plastic closure embodying the principles of the present invention includes an outer plastic cap having a top wall portion, and a depending annular skirt portion. The skirt portion includes at least one internal thread formation and may include plural, multi-lead threads.
The closure includes a disc-shaped sealing liner positioned on an inside surface of the top wall portion, with the liner configured for sealing engagement with the associated container. To this end, the liner is spaced inwardly of the annular skirt portion, and includes a depending annular sealing bead having a generally downwardly and outwardly facing sealing surface. This sealing surface is configured for sealing engagement with a generally upwardly and inwardly facing portion of the associated container, to form what is referred to as a xe2x80x9ctop/inside sealxe2x80x9d.
In accordance with the present invention, the outer plastic cap of the present closure includes at least one positive stop element engageable with the associated container. The stop element may be configured in various forms in accordance with the present invention. In accordance with one form, a plurality of circumferentially spaced stop elements depend from the inside surface of the top wall portion. In accordance with the preferred embodiment, each stop element has a generally downwardly, facing stop surface engageable with the associated container. In an alternate embodiment, the positive stop element is positioned on the closure skirt portion, preferably adjacent the thread formation of the closure for engagement with a cooperating thread formation on the associated container. When the closure is configured to include a plurality of thread formations, the closure may include a like plurality of stop elements respectively positioned adjacent the thread formations.
Features of the present closure facilitate efficient sealing with the associated container. In the preferred form, the outer plastic cap includes an annular liner support element which depends from the inside surface of the top wall portion. The support element is positioned within the annular sealing bead of the sealing liner, positioned inwardly of and generally parallel to the generally downwardly and outwardly facing sealing surface of the sealing liner. The sealing liner is preferably efficiently formed by compression molding, and preferably includes a relatively thin central panel portion, positioned inwardly of the annular sealing bead, for efficient use of liner material.
In one form, the annular stop elements depending from the inside surface of the top wall portion are positioned radially outwardly of the sealing liner, whereby each stop surface of each stop element is exposed for engagement with the associated container. In an alternate embodiment, the stop element depends from the inside surface of the top wall beneath the sealing liner, and thus cooperation with the container, while the surface of the stop element does not actually contact the container.
Other features and advantages of the present invention will become readily apparent from the following detailed description, the accompanying drawings, and the appended claims.